import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Vector;

public class CollectionsTest {
    public static void main(String[] args) {
        Collection<String> c2=new ArrayList<>();
        String[] as2={"a","b","c"};
        Collections.addAll(c2,as2);
        System.out.println(c2);
        Collections.addAll(c2,"a","b","c","d");
        System.out.println(c2);

        c2=Collections.synchronizedCollection(c2);
        c2=new Vector<>();

    }
}
